In a printing system, such as those employing laser or inkjet printers, for example, the data representing an image that is to be printed must be converted to a raster format in order for the printer print engine to be able to deposit pixels, sometimes referred to as “pels”, of toner or ink on a print media. Prior art printers include rendering systems that reside in a printer. For example, most printers include a formatter board which is a combination of hardware and firmware to accomplish this rendering task, commonly referred to as RIPping (i.e., Raster Image Processing). At a host computer, application software is used to create a digital image data file, referred to as a print job, and a print driver is used to convert the digital image to a page description language (PDL) file using well-known techniques in the art that is suitable to be transmitted to a buffer of a printer. Internally of the printer, a print data pipeline of the printer performs several operations upon the transferred print data as the print data enters the pipeline in preparation for printing. These operations include print data compression, print data decompression, color space conversion, half-toning and formatting. Typically, the various processing operations are performed by a processor under the control of printer firmware or software. The printer formatter receives the print as a PDL file and RIPs (i.e., converts) it to a format acceptable to the print engine. A corresponding electronic image is then formed on a photoconductor drum, in the case of a laser printer, which is subsequently developed and transferred to the print media to form a printed hard copy output. The formatter board is designed—with compromises dictated by user requirements and cost concerns—to convert most “typical” print jobs to the required format at a sufficient rate to allow the printer to run at its rated engine speed.
However, increasingly more and more complex graphics print jobs require longer times for the formatter board to process thus reducing the rate at which data is transferred to the print engine resulting in reduced operating speeds for the print engine and reduced production for the printer. This is particularly a problem in commercial printing or commercial printing environments where it is important for the print production operators (i.e., personnel) to run the printers at the maximum capacity for large volume print output. A common approach to address this RIP bottleneck is to perform the RIP task at the host computer. The host computer typically has much more processing power than the printer, or is more easily upgraded, and the RIP process can be performed in parallel with other printing tasks. In printing systems which provide a RIP capability at the host computer or at both the host computer and the printer, typically the decision where the RIP task is to be performed is made statically at the time of system design or installation.
On the other hand, a print system which offloads all the RIP responsibility to the host computer encounters other performance issues.
Primarily, the size of a RIPped data file can increase to many times the size of the original print job format, particularly in high resolution (1200 dpi and greater) and high quality color (e.g., 24-bit color) printing. The size of the RIPped data file for each page is also affected by the size of the print media used. While the RIPped data file can be compressed prior to being transmitted to the printer, the size of that data file can still be significant. This results in two problems: first, an increase in the transmission time over the communication link between the host computer and the printer; and second, an increase in the time required by the printer to decompress and process the large amount of data in the RIP file. While some printers provide a “video port” which accepts print data in hardware-ready bits (“HRB”), a format directly acceptable by the printer print engine, a printer which does not provide an HRB input path must accept a raster image (i.e., RIP file) which must then be reprocessed. Although the reprocessing of the RIP file by the printer does increase the time required for the overall printing process, typically it is quicker than processing PDL vector or text data directly.
Accordingly there is a need for a way to dynamically balance the responsibility RIPping and other processing of a print job data file between the host computer and the printer to efficiently utilize the capabilities of the printing system including the communication link to run the printer at the rated capacity of the print engine.